Float switch assembly

ABSTRACT

A hollow float bulb or shell is secured to a flexible electrical cord and encloses a housing which confines an electrical switch and defines a chamber with an inwardly projecting barrier. A weight member in the form of a metal ball is disposed within the chamber and rolls over the barrier to actuate the switch in response to tilting movement of the shell and housing. In one embodiment, a shuttle in the form of a metal frame is supported within the chamber for sliding movement and carries a switch conductor element. The shuttle frame is impacted by the ball located within the frame when the ball rolls over the barrier, and the frame is restrained by magnets to produce snap actuation of the switch.

BACKGROUND OF THE INVENTION

In the art of controlling a submersible pump with a float switchassembly, for example, as disclosed in U.S. Pat. Nos. 4,215,975 and4,302,641, it is common to use a hollow float bulb or shell which isadapted to float on the surface of the water or liquid being pumped. Theshell is attached to the outer free end of a flexible electrical cordwhich conducts the power for operating the pump. The float bulb or shellis fluid-tight and encloses a control switch which moves between closedand open positions in response to tilting of the float shell as theliquid level changes between predetermined upper and lower limits.

Usually, the control switch consists of a mercury actuated switch suchas disclosed in above mentioned U.S. Pat. No. 4,215,975. However, thecommonly used mercury switches are limited in the amount of currentwhich they can conduct, and this limits the size of the electric pumpmotor which can be controlled directly by a mercury switch. In addition,there is an environmental problem when it is desired to disposed of amercury switch which has failed and been replaced. Thus in place of amercury switch, it has been proposed to use a reed-type switch which isactuated by a permanent magnet movable in response to tilting of thefloat shell, for example, as disclosed in U.S. Pat. No. 4,021,144.However, such a reed switch is also limited in the amount of electricalcurrent which it can effectively conduct and is not suitable for use incontrolling relatively large horsepower submersible pumps.

SUMMARY OF THE INVENTION

The present invention is directed to an improved float switch assemblywhich is ideally suited for use in controlling an electric motor drivinga pump and which is adapted to float on the surface of the liquid beingpumped for sensing changes in the level of the surface. The switchassembly of the invention is especially suited for controlling asubmersible pump motor of substantial horsepower and provides for snapactuation of the switch in order to minimize arcing between the contactsof the switch. Thus the switch assembly of the invention provides fordependable operation without maintenance over an extended period of useand is especially suitable for controlling a motor driven pump whichmust limit the maximum liquid level within a tank or chamber.

In accordance with one embodiment of the invention, a float switchassembly includes a hollow float bulb or shell which encloses a housingmolded of a plastics material. The housing confines an electricalcontrol switch and defines a chamber which receives a weight member inthe form of a metal ball. A barrier projects inwardly into the chamber,and the ball rolls over the barrier to produce snap actuation of theswitch. In accordance with a modification of the invention, the housingsupports the frame-shaped metal shuttle which shifts axially within thehousing and confines the ball for predetermined relative movement. Theshuttle carries a switch conducting element which closes and opens theswitch when the shuttle moves within the housing in response to impactsby the ball due to tilting of the housing and the surrounding floatshell. The shuttle is retained in the switch closed position by magneticelements which are supported by the housing.

Other features and advantages of the invention will be apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial section of a float switch assembly constructed inaccordance with the invention and showing the switch in its closedposition;

FIG. 2 is an exploded perspective view of the internal components of theswitch assembly shown in FIG. 1;

FIG. 3 is a section of the switch assembly similar to FIG. 1 andillustrating the switch in its open position;

FIG. 4 is an axial section, similar to FIG. 1, of a float switchassembly constructed in accordance with a modification of the inventionand with the switch in its closed position;

FIG. 5 is another axial section of the switch assembly shown in FIG. 4and illustrating the switch in its open position; and

FIG. 6 s an elevational view of the switch assembly shown in FIGS. 1 and2 and illustrating its support and use for sensing liquid levels with ina small diameter tank or chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A switch assembly 10 is illustrated in FIG. 1 and includes a float bulbor shell 12 formed by an outer bulb section 14 coupled to an opposinginner bulb section 16 both molded of a rigid plastics material. Thesections 14 and 16 include interfitting annular portions which arecemented together to form a fluid-tight joint 17. The inner section 16of the float shell 12 includes an outwardly projecting annular hubportion 19, and the outer section 14 includes four annularly spaced ribs21 and an inwardly projecting center boss 22. The boss 22 defines anaxial hole 23 which is adapted to receive a self-tapping screw, as willbe explained later.

The float shell 12 encloses a generally cylindrical housing 25 which isformed by two mating housing sections 26 and 28 molded of a rigidplastics material and joined together by cement to form a fluid-tightjoint 31. The housing sections 26 and 28 define a generally cylindricalinternal chamber 33 and have an inwardly projecting andcircumferentially extending rib which forms a generally annular barrier34. The housing sections 26 and 28 also define two diametrically opposedand axially extending slots or grooves 36 which interrupt the rib orbarrier 34. The slots 36 extend from an outer end wall 38 of the housing25 to an inner end wall 39. A cylindrical wall 42 projects axially fromthe inner wall 39 of the housing 25 and press fits into the annular hubportion 19 of the float shell 12 so that the hub portion 19 supports theinner end portion of the housing 25 within the shell 12. The outer endportion of the housing 25 is supported by the ribs 21 which conform tothe shape of the housing, and all of the sections of the housing andshell are cemented together after the switch components are assembledwithin the housing 25.

A flexible electrical power conducting cord 45 has one end portion 46connected to the switch assembly 10 by an adhesive potting material 48,confined within the annular walls 19 and 42. The cord 45 has a pair ofwire conductors 51 which are soldered or clamped to corresponding sheetmetal conductors 52. The conductors are supported by corresponding slotsformed within the end wall 39 of the housing 25, and a switch contactelement 53 is rigidly secured to the inner end portion of each sheetmetal conductor 52.

A frame-like switch actuator or shuttle 55 is supported by the housing25 for axial sliding movement. The shuttle 55 is formed by two sheetmetal parts or stampings which are spot-welded together and have outerdiametrically opposed leg portions 56 which are slidable within thecorresponding slots 36 to provide for sliding axial movement of theshuttle 55. Each of the sheet metal parts forming the shuttle 55includes a pair of outwardly projecting flanges or tabs 58 whichcooperate to form opposing end walls or surfaces for the shuttle 55. Theinner end portion of the shuttle 55 includes welded together flat tabs61 which receive and slidably support a rectangular sheet metalconductor plate 62. The conductor plate 62 carries a pair of switchcontact elements 63 which oppose the contact elements 53, and the outerends of the tabs 61 are deformed to retain the conductor plate 62. Acompression spring 66 surrounds the tabs 61 and normally urges theconductor plate 62 outwardly on the tabs 61.

A pair of cylindrical permanent magnets 72 are cemented into the forwardend portions of the slots 36 and are effective to retain the shuttle 55in its forward or switch closed position, as shown in FIG. 1. In thisposition, the sheet metal conductors 52 are electrically connected bythe sheet metal conductor plate 62 through the contacts 53 and 63. Aweight member in the form of a stainless steel ball 75 is enclosedwithin the chamber 33 of the housing 25 and is confined within theframelike shuttle 55 for rolling movement over the rib or barrier 34.The ball 75 alternately engages the opposing parallel walls or tabs 58at opposite ends of the shuttle 55 as the ball rolls back and forthacross the barrier 34.

The operation of the switch assembly 10 is apparent from FIGS. 1 and 3.When the liquid level L being sensed by the switch assembly 10 rises toa predetermined elevation, the switch assembly tilts upwardly to apredetermined acute angle relative to a horizontal plane. In thisposition, the ball 75 rolls over the barrier 34 and impacts the innertabs 58 of the shuttle 55. This causes the shuttle to move inwardlyuntil the contacts 63 on the conductor plate 62 engage the contacts 53on the conductors 52 to close the switch and complete the circuitbetween the wire conductors 51. The closing of the switch energizes thepump motor for removing the liquid from the container or chamber whichreceives the pump and switch assembly 10.

As the liquid level L descends and reaches a predetermined lowerelevation the switch assembly 10 tilts to a downwardly inclinedposition, as shown in FIG. 3. In this position, the ball 75 rolls overthe barrier 34 again and impacts the tabs 58 on the outer end of theshuttle 55. This impact is effective to pull the shuttle from themagnets 72 and to separate the switch conductor plate 62 and contacts 63so that the switch moves to its open position, as shown in FIG. 3. Whenthe water or liquid level L rises again to the upper elevation, as shownin FIG. 1, the switch closes, and the cycle is repeated.

Referring to FIGS. 4 and 5 which show somewhat diagramatically anotherswitch assembly 80 constructed in accordance with the invention, a floatshell 82 is constructed in the same manner as the shell 12 describedabove and encloses a generally cylindrical housing 84 having an inwardlyprojecting circumferential rib forming a barrier 86. The housing 84 alsoencloses and confines a microswitch 88 having an actuator button 89operated by a pivotal lever 91 which carries a circular pad 92. Anelectrical cord 94 has a pair of flexible wire conductors 96 whichextend to the switch 88, and the connecting end portions of theconductor 96 are sealed within an enclosed corner portion of the housing84 by a potting material 98.

The cord 94 is secured to the shell 82 by a resilient tubular plug 104which extends into an inwardly projecting hub portion 106 of the shell82. A weight member in the form of a stainless steel ball 108 isconfined within the housing 84 and rolls back and forth across theinternal barrier 86 in response to tilting of the float shell 82 withchanges in the level L of the surface of the liquid being sensed by thefloat switch assembly 80.

When the bulb or shell 82 tilts upwardly (FIG. 4), the ball 108 rollsover the barrier 86 and engages the pad 92 on the switch actuating lever92 to close the switch 88. When the switch 88 tilts downwardly to theposition shown in FIG. 5, the ball 108 rolls over the barrier 86 to theouter end portion of the housing 84, and the switch 88 is released tomove to its open position. The embodiment shown in FIGS. 4 and 5 utilizea commercially available microswitch 88 which simplifies theconstruction of the assembly 10, but the switch 88 is not capable ofhandling the larger electrical load or current which may be handled bythe float switch assembly 10.

Referring to FIG. 6, the float switch assembly 10 or 80 may be used forsensing changes in the liquid level which is controlled by the length ofline between weight member 122 and the switch assembly 10. In thisembodiment, the float switch assembly 10 is positioned adjacent thedesired upper level of liquid within the tank or chamber and issupported by a V-shaped arm 115 secured to a wall or post 116. A helicalcompression or tension spring 119 surrounds the cord 45 and has an innerend portion supported by the arm 115. The outer end portion of thespring 118 projects outward from the arm 115 and allows the switchassembly 10 to pivot or tilt between an upwardly inclined closedposition, as shown in FIG. 1, and a downwardly inclined open position,as shown in FIG. 6. A buoyant weight member 122 is attached to the outerend of the switch assembly 10 by a flexible line 123, and the upper endof the line 123 is secured to the outer end of the shell 12 by a screw124 threaded into the hole 23.

As the liquid level is dropping within the chamber containing the switchassembly 10 supported as shown in FIG. 6, the coil spring 118 hassufficient strength to hold the switch assembly 10 in a horizontalposition as the liquid level drops below the switch assembly. When theliquid level L drops to an elevation where the weight member 122projects above the liquid level, the weight member 122 begins to dropwith the liquid level. The line 123 pulls downwardly on the outer end ofthe switch assembly 10 and bends the spring 118 (FIG. 6) until theswitch assembly is tilted to its downwardly inclined position whereinthe switch opens. The size and weight of the weight member 122 areselected to produce the desired actuation of the switch assembly 10, asdescribed above.

From the drawings and the above description, it is apparent that aswitch assembly constructed in accordance with the present invention,provides desirable features and advantages. For example, theconstruction of the switch assembly 10 results in producing snapactuation of the switch contacts 53 and 63 in response to tiltingmovement of the float shell 12 so that arcing between the contacts isminimized. This permits the switch assembly to handle a substantiallyhigh current so that the switch assembly is capable of controlling apump motor having substantial horsepower. The positive actuation of theshuttle 55 in response to impact by the ball 75 also assures positiveopening and closing of the switch contacts so that the switch assemblyprovides dependable operation for years of service.

The same dependable operation is provided by the embodiment shown inFIGS. 4 and 5 since the rolling movement of the ball 108 over thebarrier 88 produces positive actuation of the lever 91 of themicroswitch 88. As apparent in FIG. 4, when the switch assembly 80 is inits closed position, the ball 108 continuously presses against the lever91 as a result of the cam surface provided by the barrier 86. Thisclosing pressure is also produced by the ball 75 (FIG. 1) in the floatswitch assembly 10 to assure that the contacts 63 remain in positiveengagement with the contacts 53 when the switch assembly is closed.

While the forms of switch assembly herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope and spirit of theinvention as defined in the appended claims.

The invention having thus been described, the following is claimed:
 1. Afloat switch assembly adapted to float on a liquid surface and to sensechanges in the level of the surface for controlling a pump, saidassembly comprising a housing defining a chamber, means connected tosaid housing and forming a barrier projecting into said chamber, a setof electrical conductors extending to said housing, a shuttle supportedwithin said housing for linear movement, switch means within saidhousing and including an electrical conducting element movable by saidshuttle between a closed position connecting said conductors and an openposition, a weight member disposed within said chamber for movement oversaid barrier, means for moving said shuttle and operating said switchmeans conducting element between said open and closed positions inresponse to tilting movement of said housing and movement of said weightmember over said barrier, .Iadd.said barrier urging said weight memberagainst said shuttle in said closed position, .Iaddend.and means forfloating said housing on the liquid surface.
 2. A float switch assemblyas defined in claim 1 wherein said weight member comprises a ball, andsaid barrier comprises a generally annular portion of said housing.
 3. Afloat switch assembly as defined in claim 1 wherein said floating meanscomprise a hollow float shell surrounding said housing, and said shellincludes means supporting said housing within said shell.
 4. A floatswitch assembly as defined in claim 1 wherein said shuttle comprises aframe surrounding said weight member, and said weight member comprises aball disposed within said frame for relative movement.
 5. A float switchassembly as defined in claim 4 and including magnetic means supported bysaid housing for retaining said frame in a position corresponding tosaid switch means in said closed position.
 6. A float switch assembly asdefined in claim 5 wherein said magnetic means comprise a pair of spacedpermanent magnets disposed within opposing slots supporting said framefor linear movement.
 7. A float switch assembly as defined in claim 1and including means for tilting said housing after the liquid surfacedrops substantially below said housing.
 8. A float switch assembly asdefined in claim 2 wherein said shuttle comprises a frame defining anopenng therein, said barrier projects towards said opening, and saidball is disposed within said opening for rolling movement over saidbarrier.
 9. A float switch assembly as defined in claim 1 wherein saidhousing includes internal guide means supporting said shuttle forsliding linear movement within said housing.
 10. A float switch assemblyas defined in claim 1 and including means for retaining said shuttle insaid closed position until said housing is tilted to a predeterminedacute angle relative to a horizontal plane.
 11. A float switch assemblyas defined in claim 1 wherein said electrical conducting elementcomprises a metal contact element, and said shuttle includes meanssupporting said contact element for movement with said shuttle and forslight movement relative to said shuttle.
 12. A float switch assembly asdefined in claim 1 wherein said floating means comprise a hollow floatshell surrounding said housing and defining a space therebetween, meansfor securing said housing to said shell for supporting said housingwithin said shell, and means connecting said electrical conductors tosaid shell and forming a fluid-tight seal therebetween.
 13. A floatswitch assembly as defined in claim 12 wherein said shell comprisesfirst and second cup-shaped sections in opposing relation, said housingis mounted on first section of said shell, and means connecting saidfirst and second sections of said shell together and forming afluid-tight seal therebetween.
 14. A float switch assembly adapted tofloat on a liquid surface and to sense changes in the level of thesurface for controlling a pump, said assembly comprising a housingdefining a generally cylindrical chamber, means connected to saidhousing and forming a generally annular barrier projecting into saidchamber, a set of electrical conductors extending to said housing,switch means within said housing and connected to said conductors, meansfor actuating said switch means between a closed position connectingsaid conductors and an open position disconnecting said conductors, aball member disposed within said chamber and movable over said barrierto operate said actuating means in response to tilting movement of saidhousing and independent of the rotational position of said housing,means for floating said housing on the liquid surface, a flexible powercord including said electrical conductors and supporting said floatingmeans for said tilting and rotational movement of said housing .[.and.]..Iadd., .Iaddend.said ball member having a diameter substantiallysmaller than the diameter of said generally cylindrical chamber .Iadd.,and said barrier urges said ball member against said actuating means inone of said positions. .Iaddend.
 15. A float switch assembly as definedin claim 14 wherein said switch means compise a microswitch disposedwithin said housing and having a pivotal actuating lever, and saidbarrier presses said ball member against said lever when said housing istilted.
 16. A float switch assembly as defined in claim 14 wherein saidfloating means comprise a hollow float shell surrounding said housing,and said shell includes means supporting said housing within said shell.17. A float switch assembly as defined in claim 14 and including meansfor tilting said housing after the liquid surface drops substantiallybelow said housing. .[.18. A float switch assembly as defined in claim14 wherein said barrier urges aid ball member against saiad actuatingmeans in one of said positions..].